Electronic digital watches are so called because they provide a digital read-out of time, and can be worn by the user on his wrist in the usual manner. Unlike conventional watches, however, electronic digital watches have substantially no moving parts, no clockwork assemblies and no crown and stem assemblies. An electronic digital watch may have no continuous read-out or display if it is of the light-emitting diode (LED) type; or it may if it is of the liquid crystal display (LCD) type. In any event, such a watch may provide an indication of the time, or of continuous running of time in seconds, or of date, upon actuation of one or more controls by the user.
Normally, the controls of an electronic digital watch comprise an activator post which extends out from the side of the watch case in which the outer components are enclosed, and a buttom may be affixed to the outer end of the activator post for ease of contact by a finger of the user. When the user wishes to refer to his electronic digital watch for a particular indication of time or date, the appropriate activator button or buttons are pressed the required number of times by the user, and the required output is digitally displayed. Obviously, when no particular digital display is required, the watch must be such that the activator posts are not in an actuated condition. For this reason, the activator posts of an electronic digital watch function essentially as a momentary make switch. Subsidiary electronic circuits are provided within the watch so that, upon actuation of an activator button, one of those circuits is energized and the appropriate read-out is displayed. One or a plurality (usually two) of energy cells or batteries are included in the watch case, and are retained in operating contact with the electronic module by suitable spring means. The subsidiary, read-out circuits, are activated by the operation of the appropriate activator button against a switch element contained within the watch case, so as to close the electric circuit from the battery, through the watch case, the activator post which contacts the switch element, and the switch element to the electronic module. The activator post is, accordingly, spring-loaded or otherwise spring mounted so that it can be operated only by exerting pressure against its outer end beyond a pre-determined pressure, so as to close the appropriate subsidiary circuit; and release of the pressure against the activator post and activator button is followed by a return of the activator post to its normal position out of contact with the activator switch element. Thus, a momentary make switch is provided for each activator button and activator post included in the electronic digital watch.
Because, in the past, the casings of the electronic digital watches have had to be electrically conductive in order to ensure that at least the subsidiary electrical circuits which are operable by the user upon activation of one of the activator buttons, such casings have been expensive to produce and have had limited styling possibilities.
The present invention, therefore, provides a means whereby quite inexpensive watch cases for electronic digital watches may be designed having any desired exterior styling characteristics or shape, provided only that the interior of the watch case is appropriately dimensioned so as to receive the essential elements of the watch. This may be accomplished by casting or molding the watch cases using a suitable plastic material. However, any such suitable plastics material is substantially electrically non-conductive, and the present invention provides a retainer casing to be included within the watch case so as to retain the batteries in operating position within the case, and also so as to retain the activator posts in the appropriate manner so that each may be operated as a momentary make switch in the usual manner.
This is accomplished by providing an electrically conductive retainer casing within the substantially electrically non-conductive watch case. In general terms, the electrically conductive retainer casing is one which has a substantially planar bottom, and is adapted to contact and to exert and maintain spring pressure against the battery or batteries which are placed on the underside of the electronic and digital display module. The retainer casing has at least a portion thereof which is upstanding from the bottom of the casing at its edge, and that portion is adapted to retain the inner end of the activator post with which it is associated in such a position that it is out of a co-operating position with respect to the activator switch element on the digital display module. Thus, the inner end of the activator post is kept out of a position which would result in a closing action of the switch element so as to cause a particular digital read-out as determined by actuation of the activator button and post. At least a pre-determined force must, therefore, be exerted axially along the activator post from the button or the outer end of the post; and it will be noted, therefore, that at least the portion of the retainer casing which is co-operating with the inner end of each activator post is such that it is flexible and has an elastic memory so as to be temporarily deformable. Thus, when at least the pre-determined force is exerted axially along the activator post, the inner end of the post acts against the elastic memory of the portion of the retainer casing so as to move into a co-operating position with respect to the activator switch element, thereby causing an electrical circuit to be formed at least from the battery to the activator switch element through the retainer casing. When the axial force on the activator post is released, the elastic memory of the retainer casing portion causes the activator post to move out of the co-operating position with respect to the activator switch element.
Where the electrically conductive retainer casing is metallic or a metal coated plastic material, it may have at least one tab upstanding substantially perpendicularly from the bottom thereof and at the edge thereof, and being formed in a manner so as to retain the inner end of the activator post out of contact with its respective activator switch element. Thus, the retainer tab is flexible but requires a pre-determined pressure against the outer end of the activator post and axially therealong so as to cause the tab to temporarily deform sufficiently that the electrical circuit may be constituted, either through the end of the activator post or by the tab itself. Upwardly extending spring tabs may be formed in the bottom of the retainer casing, and are adapted to contact and maintain spring pressure against the battery so as to maintain it in electrical contact with the electronic module.
In the preferred embodiments of such a retainer casing, as discussed hereafter, a plurality of tabs is formed at the edge of the retainer casing in designated places so that the retainer casing can be used for a number of different designs of watches. Usually the activator posts and activator buttons are spaced apart by designated arcs subtended at the center of the operating and display module, so that relatively few operating and display modules need to be designated, regardless of the design of the watch case per se. In this manner, manufacture of the operating and display modules can be retained by the electronics industries, and a variety of brands and designs of electronic digital watches may be sold in the retail market, all having identical operating and display modules. In one alternative arrangement, the tabs are also used for orienting, positioning and retaining and components within the watch case.
It is usual to provide at least two activator buttons and activator posts for each electronic digital watch; one to activate the digital display and to determine what function is to be displayed, and the other to provide primary settings of time and date, and for adjustments of the display in the event of short months, movement from one time zone to another by the user, etc.
Yet another embodiment of the retainer casing is provided, as discussed hereafter, whereby the entire casing comprises a pre-formed shell and is formed of an electrically conductive elastomeric material. In this case, the battery and the electronic and display module are secured within the retainer casing shell, such as by the co-operation of an inwardly turned lip when the shell is substantially cup-shaped. The inner end of the activator post is retained in its position by the inherent elasticity of the side of the elastomeric retainer casing, but in such a manner that the inside surface of the side of the retainer casing is not in contact with a respective activator switch element on the electronic and display module. Force exerted axially along the activator post, in the usual manner, causes sufficient deformation of the material of the side of the retainer casing that the inside surface thereof is brought into contact with the activator switch element, thereby closing an electrical circuit from the battery through the electrically conductive elastomeric material to the switch element.
In the preferred embodiment of the elastomeric retainer casing, an additional metal-coated plastic or metallic insert is placed within the shell between the bottom thereof and the underside of the electronic operating module, and the insert is formed with at least one spring tab which is upwardly extending from the insert towards the battery (or at least one such tab for each battery) so as to assure that electrical contact and spring pressure are maintained against the battery.